US 7599561 B2
The subject application relates to a system(s) and/or methodology that facilitate vision-based projection of any image (still or moving) onto any surface. In particular, a front-projected computer vision-based interactive surface system is provided which uses a new commercially available projection technology to obtain a compact, self-contained form factor. The subject configuration addresses installation, calibration, and portability issues that are primary concerns in most vision-based table systems.
1. A projection-vision system that facilitates sensing and projecting objects as images, comprising:
a projection surface on which at least one visual coded image is presented; and
an object sensing component, executed by a processor and stored in memory, that detects that the visual coded image is present on the projection surface by:
computing an edge intensity and edge orientation for each pixel in the at least one visual coded image;
using the edge intensity and edge orientation to determine code values for each pixel; and
obtaining a candidate instance of the code by checking the code values against a table of codes, and if a match exists, the match is the candidate instance of the code.
2. The system of
establishing a rotated local coordinate system utilizing the edge orientation for each pixel with a high edge intensity;
reading each pixel value in a rectified image in the rotated local coordinate system, each pixel value in the rectified image corresponds to each bit in a code; and
determining a code value by thresholding each pixel based on a minimum and maximum pixel value read.
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The advent of novel sensing and display technology has encouraged the development of a variety of interactive systems which move the input and display capabilities of computing systems on to everyday surfaces such as walls and tables. The manner in which this has been done in current systems indicates an attempt to address design and integration objectives. However, such systems remain deficient in their variety of sensing capabilities, suitability to easy installation and calibration, and/or usability of the systems among consumers.
The following presents a simplified summary in order to provide a basic understanding of some aspects of the systems and/or methods discussed herein. This summary is not an extensive overview of the systems and/or methods discussed herein. It is not intended to identify key/critical elements or to delineate the scope of such systems and/or methods. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.
The subject application relates to a system(s) and/or methodology that facilitate sensing of objects and co-location of projection of any image (still or moving) onto any surface. In particular, a front-projected computer vision-based interactive table system is provided which uses a new commercially available projection technology to obtain a compact, self-contained form factor. The subject configuration addresses installation, calibration, and portability issues that are primary concerns in most vision-based table systems. More specifically, the projector and cameras, as well as computing resources such as CPU and storage, can be built into the same compact device. This combined projecting and sensing pod may be readily placed on any flat surface in the user's environment and requires no calibration of the projection or sensing system. It is this portability, ease of installation, and ability to utilize any available surface without calibration that tends to be more important or even required for mainstream consumer acceptance. For example, imagine a child pulling such a device out of the closet and placing it on a table or the floor of their room to transform the nearby surface into an active play, school work, or entertainment space.
The subject system is capable of sensing a variety of objects and displaying animated graphics over a large display surface and uses a new commercially available projection technology to obtain an exceptionally compact, self-contained form factor. Unlike many other conventional systems, this system may be quickly set up to operate on any flat surface, requires no calibration beyond the factory, and is compact while still displaying and sensing over a large surface area such as a wall, floor, or elevated surface (e.g., platform, table, or desk). These features make it especially attractive in consumer applications, where distribution, installation, mounting, and calibration considerations tend to be paramount.
Furthermore, image processing techniques for front-projected vision-based table systems are also provided. These techniques include a shadow-based touch detection algorithm, a fast and uncomplicated visual bar code scheme tailored to projection-vision table systems, the ability to continuously track sheets of paper, and an optical flow-based algorithm for the manipulation of onscreen objects that does not rely on fragile tracking algorithms.
To the accomplishment of the foregoing and related ends, certain illustrative aspects of the invention are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the subject invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention may become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
The subject systems and/or methods are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the systems and/or methods. It may be evident, however, that the subject systems and/or methods may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing them.
As used herein, the terms “component” and “system” are intended to refer to a computer-related entity, either hardware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and a computer. By way of illustration, both an application running on a server and the server can be a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers.
Referring now to
By configuring the system as a single unit, it can be made compact and more portable for user convenience. With portable projection systems, one thought that often comes to mind is calibration—or rather re-calibration which is often required in a conventional projection system after the system is moved. However, in an exemplary configuration of the subject system 100 as represented in
The NEC WT600 is an unusual projector in that it uses four aspheric mirrors (no lenses) to project a normal 1024×768 rectangular image from a very oblique angle, and at extremely short distance. For a 40″ diagonal image, the WT600 requires 2.5″ between its leading face and the projection surface, while a 100″ diagonal image is obtained at a distance of 26″. These characteristics make it very well suited for the system 100, in that it allows for the projector to sit directly on the projection surface (on a short pedestal), rather than be hung suspended over the surface.
As in other projection-vision systems, the scene (display space) can be illuminated with an infrared source and all but infrared light can be blocked to the camera with an infrared-pass filter. This effectively removes the projected image from the scene. The projector provides a natural place to mount one or more cameras and an infrared illuminant. By rigidly mounting the cameras and illuminant to the projector, the calibration of the vision system to the display is the same regardless of where the unit is situated and may be determined at the factory.
One method to perform sensing and detection of objects on the surface is to use two cameras and simple stereo calculations as has been done in traditional systems, but in the subject system 100, one camera is employed combined with image techniques that allow touch detection by examining the shadows of objects, detailed later in
Once configured, the camera-projection component 110 can project images onto a display surface 120. The images can be rectified by way of an image processor component 130 and then displayed as a display image. The rectification process can involve performing calculations on an input image. Any calculations made on the image by the image processor component can be related directly to the displayed image. That is, a tracked position in the rectified image can be readily mapped to the corresponding position in the displayed image. For example, rectification can be employed to remove any undesirable distortion from the input image. In practice, the camera-projection system can utilize a wide angle lens which can impart significant barrel distortion on the input image; while the oblique position of the camera imparts a projective distortion or foreshortening. The image processor component 130 can remove both distortions via standard bilinear interpolation techniques. Parameters necessary to correct for lens distortion can be recovered by an off-line procedure.
The projective transform is determined by finding each of the four corners of the projected display by placing infrared reflective markers (paper) on the surface at known locations indicated by the projected image. Image rectification is illustrated in
Any objects placed on or hovering over the display surface can be detected, recognized, and/or tracked using the image processor component 130. In particular, the image processor component 130 can detect objects touching the surface without relying on special instrumentation of, underlying, or on the surface. Thus, the system 100 can operate on any flat surface. More detailed information regarding the image processor component 130 can be found in the discussion for
Turning now to
The top-down approach in 310 is rather popular since such mounting considerations are often necessary due to the throw requirements of projectors and the typical focal length of video cameras. However, ceiling installation of a heavy projector can be more than challenging, dangerous, can require special mounting hardware not easily accessible by most consumers, and for all practical purposes may be best left to professional installers, which involves additional costs and less accessibility to the general public. Once installed, this top-down system and projection surface cannot be readily moved without requiring tedious or time-consuming re-calibration of the system. In addition, minor vibrations present in many buildings can create problems during operation and can make it difficult to maintain calibration. There is also a possibility of occlusion of the projected image by a user's head and/or hands as they interact with the top-down system.
A second common approach is the rear projection set-up (320) wherein the projector and camera are placed behind a diffuse projection screen. While this enables the construction of a self-contained device, eliminates some occlusion problems, and permits the placement of visual codes on the bottom of objects, it is challenging at best to construct such a configuration with a large display area that also provides users with sufficient room to put their legs under the table surface so that they may sit comfortably at the table. Furthermore, a dedicated surface is required and the resulting housing for the projector and camera can be quite large and thus cumbersome and inconvenient for “anywhere” consumer use. It also presents significant manufacturing and production problems which may hinder yielding a marketable product.
Contrary to these common approaches, the subject configuration 330 employs a camera and projector sitting off to the side of the active (projection) surface which mitigates many if not all of the drawbacks associated with typical projection-vision systems. In fact, the application of this projector has a number of advantages. First, it avoids the often difficult and dangerous overhead installation of the projector. Second, it is reasonable to assume that the plane of the surface holding the projector is the projection plane. If the camera and illuminant are rigidly mounted to the projector as shown in
Furthermore, with the oblique projection, occlusion problems typical of conventional front-projected systems are minimized. For example, it is possible for the user to stand over the system without their head occluding the projected image. Finally, a 40″ diagonal projection surface which can be offered by the system is adequate for many advanced interactive table applications, including complex gaming scenarios that go beyond simple board games and manipulation of multiple photos, printed pages, etc.
As previously mentioned,
Turning now to
Visual codes have been applied in various augmented reality and table scenarios, where they can be used to identify potentially any object large enough to bear the code without recourse to complex generalized object recognition techniques. In tabletop, floor, or even wall scenarios, for instance, such visual codes are especially useful to locate and identify game pieces, printed pages, media containers, knobs, and other objects that are generic in appearance but may vary in application semantics. As a knob, for example, an identified piece could adjust the color and contrast of a digital photo. A number of visual code schemes are used in augmented reality research. Here, a code format and algorithm designed for the systems discussed herein is outlined. This code is particularly fast and can be implemented on GPU hardware currently available and requires no search to determine code orientation. Generally the problem of designing a code format is one of balancing the opposing goals of obtaining a simple detection algorithm that works with the various transformations observed (e.g., translation, rotation) while supporting a useful number of code bits.
In the case of calibrated tabletop (or any other surface) vision systems, including the subject system, where we may be interested in game pieces on the surface, for example, the system can assume that each instance of the code appears in the image with known, fixed dimensions, thus simplifying the recognition and decoding process. The design of the subject code, illustrated in
In practice, depending on the code bit depth, the number of application code values required and the nature of potential distracters in the image, it may be necessary to add a further step that verifies the instance. For example, consideration of image locations can be limited to those that appear to be the center of circular contours of the game piece diameter. Such contours can be found quickly using the Hough transform applied to circles, reusing the edge orientation information computed above: a 2D histogram (image) representing the presence of circles centered at a given point is created by, for each pixel in the input image, calculating the center of the circle of a given radius and edge orientation found at the input coordinates, and incrementing the histogram at the calculated center. Each point in the resulting histogram indicates the likelihood of a circle of the given radius centered there.
The object sensing component 510 can also include an object tracking component 540 that can track the movement of objects in real-time on the projection surface 520. In particular, real objects can be captured and when detected, can cause their corresponding virtual objects to be projected on the surface 520 for further manipulation or modification. For example, consider making a real charcoal drawing on paper. This drawing could then be captured to an image precisely using the page tracking information, and then later projected back onto the surface as a virtual object, or even onto a blank piece of paper, or another work in progress.
For instance, with regard to page tracking, the object tracking component 540 can employ a page tracking algorithm that is based on a Hough transform with the Sobel edge and orientation information as input. This gives a histogram over orientation and perpendicular distance to the origin which indicates the presence of strong lines in the image. Given the dimensions of a page size to detect, it is straightforward to find appropriate pairs of parallel lines a set distance apart. Two pair of parallel lines perpendicular to each other is verified as a page by ensuring that there are strong edges along a significant fraction of the lines in the original Sobel image. This proportion can be tuned to allow for pages to overlap (e.g.,
Turning now to
Finger tracking may be performed however it would require making some assumptions about the appearance of the surface and fingers (e.g., that fingers and the surface have significantly different brightness). With shadow analysis, recovering the shadow reliably requires only that the surface reflect infrared and that the device's infrared illuminant is significantly brighter than stray infrared in the environment. Both assumptions are reasonable given that the user is likely to place the device on a surface where the projection has good contrast and brightness (e.g., not on a black surface or in a very bright room). A shadow image can be computed from the rectified input by a simple thresholding operation (see
The images in
Various methodologies will now be described via a series of acts. It is to be understood and appreciated that the subject system and/or methodology is not limited by the order of acts, as some acts may, in accordance with the subject application, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with the subject application.
Turning now to
Moreover, the projection-vision system as described herein offers a compact and readily portable unit that can be moved during use without requiring re-calibration of the system. The system can be employed for work, play, entertainment, or any other purpose. The exemplary configurations of the system are included merely for demonstration of the various components arranged in a single unit but are not meant to limit the system to a particular size, dimension, or configuration. Processors and memory storage can also be included in the configuration. When put into use, the projection-vision system can project virtual representations of items or objects and permit manipulation or other interaction of them by one or more users. Thus, the projection surface becomes an interactive surface, allowing users to perform various computing operations, content modification, and navigation of the projected content such as panning, zooming, and scrolling. In particular, flow field technology can be employed or integrated with the projection-vision system to facilitate such navigational techniques when viewing projected images (e.g., map, architectural plans, etc.)
In order to provide additional context for various aspects of the subject invention,
Generally, however, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular data types. The operating environment 1410 is only one example of a suitable operating environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Other well known computer systems, environments, and/or configurations that may be suitable for use with the invention include but are not limited to, personal computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include the above systems or devices, and the like.
With reference to
The system bus 1418 can be any of several types of bus structure(s) including the memory bus or memory controller, a peripheral bus or external bus, and/or a local bus using any variety of available bus architectures including, but not limited to, 11-bit bus, Industrial Standard Architecture (ISA), Micro-Channel Architecture (MCA), Extended ISA (EISA), Intelligent Drive Electronics (IDE), VESA Local Bus (VLB), Peripheral Component Interconnect (PCI), Universal Serial Bus (USB), Advanced Graphics Port (AGP), Personal Computer Memory Card International Association bus (PCMCIA), and Small Computer Systems Interface (SCSI).
The system memory 1416 includes volatile memory 1420 and nonvolatile memory 1422. The basic input/output system (BIOS), containing the basic routines to transfer information between elements within the computer 1412, such as during start-up, is stored in nonvolatile memory 1422. By way of illustration, and not limitation, nonvolatile memory 1422 can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM), or flash memory. Volatile memory 1420 includes random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).
Computer 1412 also includes removable/nonremovable, volatile/nonvolatile computer storage media.
It is to be appreciated that
A user enters commands or information into the computer 1412 through input device(s) 1436. Input devices 1436 include, but are not limited to, a pointing device such as a mouse, trackball, stylus, touch pad, keyboard, microphone, joystick, game pad, satellite dish, scanner, TV tuner card, digital camera, digital video camera, web camera, and the like. These and other input devices connect to the processing unit 1414 through the system bus 1418 via interface port(s) 1438. Interface port(s) 1438 include, for example, a serial port, a parallel port, a game port, and a universal serial bus (USB). Output device(s) 1440 use some of the same type of ports as input device(s) 1436. Thus, for example, a USB port may be used to provide input to computer 1412, and to output information from computer 1412 to an output device 1440. Output adapter 1442 is provided to illustrate that there are some output devices 1440 like monitors, speakers, and printers among other output devices 1440 that require special adapters. The output adapters 1442 include, by way of illustration and not limitation, video and sound cards that provide a means of connection between the output device 1440 and the system bus 1418. It should be noted that other devices and/or systems of devices provide both input and output capabilities such as remote computer(s) 1444.
Computer 1412 can operate in a networked environment using logical connections to one or more remote computers, such as remote computer(s) 1444. The remote computer(s) 1444 can be a personal computer, a server, a router, a network PC, a workstation, a microprocessor based appliance, a peer device or other common network node and the like, and typically includes many or all of the elements described relative to computer 1412. For purposes of brevity, only a memory storage device 1446 is illustrated with remote computer(s) 1444. Remote computer(s) 1444 is logically connected to computer 1412 through a network interface 1448 and then physically connected via communication connection 1450. Network interface 1448 encompasses communication networks such as local-area networks (LAN) and wide-area networks (WAN). LAN technologies include Fiber Distributed Data Interface (FDDI), Copper Distributed Data Interface (CDDI), Ethernet/IEEE 1102.3, Token Ring/IEEE 1102.5 and the like. WAN technologies include, but are not limited to, point-to-point links, circuit switching networks like Integrated Services Digital Networks (ISDN) and variations thereon, packet switching networks, and Digital Subscriber Lines (DSL).
Communication connection(s) 1450 refers to the hardware/software employed to connect the network interface 1448 to the bus 1418. While communication connection 1450 is shown for illustrative clarity inside computer 1412, it can also be external to computer 1412. The hardware/software necessary for connection to the network interface 1448 includes, for exemplary purposes only, internal and external technologies such as, modems including regular telephone grade modems, cable modems and DSL modems, ISDN adapters, and Ethernet cards.
What has been described above includes examples of the subject system and/or method. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the subject system and/or method, but one of ordinary skill in the art may recognize that many further combinations and permutations of the subject system and/or method are possible. Accordingly, the subject system and/or method are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.